Herbage utilisation method affects rumen fluid and milk fatty acid profile in Holstein and Montbéliarde cows

Compared with maize silage- and concentrate-based diets, herbage-based diets were repeatedly shown to favourably influence the milk fatty acid (FA) profile. However, it is unclear how the herbage feeding mode (grazing vs indoor green-feeding) and conservation (fresh herbage vs hay vs silage) modify the milk FA profile. Therefore, the aim of the present experiment was to investigate the effect of different herbage utilisation methods (including herbage feeding mode and herbage conservation method) on the ruminal biohydrogenation of dietary FA and the consequences on the milk FA composition in cows of two breeds (Holstein and Montbéliarde). Concomitant effects of botanical composition and phenological stage of the herbage on milk FA profile were controlled for by harvesting barn-dried hay and silage simultaneously as first cut from the same ryegrass-dominated grassland in a semi-mountainous region. Seven weeks later, the first regrowth of the same plot was used as fresh herbage, either grazed or fed indoor (indoor green-feeding). Twenty-four Montbéliarde and 24 Holstein cows were randomly allocated to four groups of 12 cows balanced by breed, parity, and milk yield. In a free-stall barn, three groups were given ad libitum access to hay, silage, or fresh herbage, respectively. The fourth group was strip-grazing. All cows were supplemented with 3 kg DM/day of the same energy-rich concentrate. After 2 weeks of adaptation to the forage, samples of forage, concentrate, milk, blood, and rumen fluid were collected. Fatty acid composition of forages, rumen fluid, and milk was analysed by gas chromatography. Haymaking reduced total FA content of the herbage, in particular that of linoleic acid (LA) and α-linolenic acid (ALA). Still, rumen fluid lipids of hay-fed cows had the highest proportion of rumenic acid, LA, ALA, and total polyunsaturated fatty acids (PUFAs). Milk fat from hay-fed cows had the highest proportion of LA, and the apparent transfer rates from feed to milk of LA and ALA were higher in hay-fed cows than in silage-fed cows. The proportion of PUFAs was highest in milk fat from grazing and indoor green-fed Montbéliarde cows and lowest in silage-fed cows of both breeds. In conclusion, the herbage utilisation method affects the ruminal biohydrogenation of LA and ALA, whereby herbage drying particularly increases their transfer from herbage to milk.     

Effect of perennial ryegrass (Lolium perenne L.) cultivars on the milk yield of grazing dairy cows

The objective of this experiment was to investigate the effect of four perennial ryegrass cultivars: Bealey, Astonenergy, Spelga and AberMagic on the milk yield and milk composition of grazing dairy cows. Two 4 × 4 latin square experiments were completed, one during the reproductive and the other during the vegetative growth phase of the cultivars. Thirty-two Holstein–Friesian dairy cows were divided into four groups, with each group assigned 17 days on each cultivar during both experiments. Within each observation period, milk yield and milk composition, sward morphology and pasture chemical composition were measured. During the reproductive growth phase, organic matter digestibility (OMD) was greater for Bealey and Astonenergy (P < 0.001; +1.6%). AberMagic contained a higher stem proportion (P < 0.01; +0.06) and a longer sheath height (P < 0.001; +1.9 cm). Consequently, cows grazing AberMagic recorded a lower milk yield (P < 0.001; −1.5 kg/day) and a lower milk solids yield (P < 0.001; −0.13 kg/day). During the vegetative growth phase, OMD was greater (P < 0.001; +1.1%) for Bealey, whereas the differences between the cultivars in terms of sward structure were smaller and did not appear to influence animal performance. As a result, cows grazing Bealey recorded a higher milk yield (P < 0.001; +0.9 kg/day) and a higher milk solids yield (P < 0.01; +0.08 kg/day). It was concluded that grass cultivar did influence milk yield due to variations in sward structure and chemical composition.     

Effects of ewes grazing sulla or ryegrass pasture for different daily durations on forage intake,milk production and fatty acid composition of cheese

Sulla (Sulla coronarium L.) forage is valued for its positive impact on ruminant production, in part due to its moderate content of condensed tannin (CT). The duration of daily grazing is a factor affecting the feed intake and milk production of ewes. In this study, the effects of grazing sulla pasture compared with annual ryegrass, and the extension of grazing from 8 to 22 h/day, were evaluated with regard to ewe forage intake and milk production, as well as the physicochemical properties and fatty acid (FA) composition of cheese. During 42 days in the spring, 28 ewes of the Comisana breed were divided into four groups (S8, S22, R8 and R22) that grazed sulla (S) or ryegrass (R) for 8 (0800 to 1600 h) or 22 h/day, and received no feeding supplement. In six cheese-making sessions, cheeses were manufactured from the 48 h bulk milk of each group. Compared with ewes grazing ryegrass, those grazing sulla had higher dry matter (DM) intake, intake rate and milk yield, and produced milk that was lower in fat and higher in casein. Ewes grazing for 22 h spent more time eating, which reduced the intake rate, increased DM and nutrient intake and milk yield, and reduced milk fat. Due to the ability of CT to inhibit the complete ruminal biohydrogenation of polyunsaturated fatty acids (PUFA), the FA composition of sulla cheese was more beneficial for consumer health compared with ryegrass cheese, having lower levels of saturated fatty acids and higher levels of PUFA and n-3 FA. The FA profile of S8 cheese was better than that of S22 cheese, as it was higher in branched-chain FA, monounsaturated FA, PUFA, rumenic acid (c9,t11-C18:2), and had a greater health-promoting index. The effect of short grazing time on sulla was attributed to major inhibition of PUFA biohydrogenating ruminal bacteria, presumably stimulated by the higher accumulation of sulla CT in the rumen, which is related to a higher intake rate over a shorter eating time. Thus, grazing sulla improved the performance of ewes, thereby increasing, especially with short grazing time, the nutritional properties of cheese fat.     

Effect of timing of corn silage supplementation to Holstein dairy cows given limited daily access to pasture: intake and performance

The timing in which supplements are provided in grazing systems can affect dry matter (DM) intake and productive performance. The objective of this study was to evaluate the effect of timing of corn silage supplementation on ingestive behaviour, DM intake, milk yield and composition in grazing dairy cows. In total, 33 Holstein dairy cows in a randomized block design grazed on a second-year mixed grass–legume pasture from 0900 to 1500 h and received 2.7 kg of a commercial supplement at each milking. Paddock sizes were adjusted to provide a daily herbage allowance of 15 kg DM/cow determined at ground level. The three treatments imposed each provided 3.8 kg DM/day of corn silage offered in a single meal at 0800 h (Treatment AM), equally distributed in two meals 0800 and 1700 h (Treatment AM-PM) or a single meal at 1700 h (Treatment PM). The experiment was carried out during the late autumn and early winter period, with 1 week of adaptation and 6 weeks of measurements. There were no differences between treatments in milk yield, but 4% fat-corrected milk yield tended to be greater in AM-PM than in AM cows, which did not differ from PM (23.7, 25.3 and 24.6±0.84 kg/day for AM, AM-PM and PM, respectively). Fat percentage and yield were greater for AM-PM than for AM cows and intermediate for PM cows (3.89 v. 3.66±0.072% and 1.00 v. 0.92±0.035 kg/day, respectively). Offering corn silage in two meals had an effect on herbage DM intake which was greater for AM-PM than AM cows and was intermediate in PM cows (8.5, 11.0 and 10.3±0.68 kg/day for AM, AM-PM and PM, respectively). During the 6-h period at pasture, the overall proportion of observations on which cows were grazing tended to be different between treatments and a clear grazing pattern along the grazing session (1-h observation period) was identified. During the time at pasture, the proportion of observations during which cows ruminated was positively correlated with the DM intake of corn silage immediately before turn out to pasture. The treatment effects on herbage DM intake did not sufficiently explain differences in productive performance. This suggests that the timing of the corn silage supplementation affected rumen kinetics and likewise the appearance of hunger and satiety signals as indicated by observed changes in temporal patterns of grazing and ruminating activities.     

e-Cow: an animal model that predicts herbage intake, milk yield and live weight change in dairy cows grazing temperate pastures, with and without supplementary feeding

This animal simulation model, named e-Cow, represents a single dairy cow at grazing. The model integrates algorithms from three previously published models: a model that predicts herbage dry matter (DM) intake by grazing dairy cows, a mammary gland model that predicts potential milk yield and a body lipid model that predicts genetically driven live weight (LW) and body condition score (BCS). Both nutritional and genetic drives are accounted for in the prediction of energy intake and its partitioning. The main inputs are herbage allowance (HA; kg DM offered/cow per day), metabolisable energy and NDF concentrations in herbage and supplements, supplements offered (kg DM/cow per day), type of pasture (ryegrass or lucerne), days in milk, days pregnant, lactation number, BCS and LW at calving, breed or strain of cow and genetic merit, that is, potential yields of milk, fat and protein. Separate equations are used to predict herbage intake, depending on the cutting heights at which HA is expressed. The e-Cow model is written in Visual Basic programming language within Microsoft Excel^R. The model predicts whole-lactation performance of dairy cows on a daily basis, and the main outputs are the daily and annual DM intake, milk yield and changes in BCS and LW. In the e-Cow model, neither herbage DM intake nor milk yield or LW change are needed as inputs; instead, they are predicted by the e-Cow model. The e-Cow model was validated against experimental data for Holstein–Friesian cows with both North American (NA) and New Zealand (NZ) genetics grazing ryegrass-based pastures, with or without supplementary feeding and for three complete lactations, divided into weekly periods. The model was able to predict animal performance with satisfactory accuracy, with concordance correlation coefficients of 0.81, 0.76 and 0.62 for herbage DM intake, milk yield and LW change, respectively. Simulations performed with the model showed that it is sensitive to genotype by feeding environment interactions. The e-Cow model tended to overestimate the milk yield of NA genotype cows at low milk yields, while it underestimated the milk yield of NZ genotype cows at high milk yields. The approach used to define the potential milk yield of the cow and equations used to predict herbage DM intake make the model applicable for predictions in countries with temperate pastures.     

Effect of time at pasture combined with restricted indoor feeding on production and behaviour in dairy cows

Extremely high nutrient loads have been reported in grazed grassland regimes compared with cutting regimes in some dairy systems that include the use of supplemental feeding. The aim of this study was, therefore, to investigate the effects on productivity and behaviour of high-yielding dairy cows with limited access to indoor feed and restriction in the time at pasture in a continuous stocking system. During a 6-week period from the start of the grazing season 2005, an experiment was conducted with the aim of investigating the effect of restrictive indoor feeding combined with limiting the time at pasture on the productivity and behaviour of high-yielding dairy cows (31.0 ± 5.4 kg energy-corrected milk) in a system based on continuous stocking. The herd was split into three groups allocated to three treatments consisting of 4, 6.5 and 9 h at pasture, respectively. Each group of cows grazed in separate paddocks with three replicates and was separately housed in a cubicle system with slatted floor during the rest of the day. All cows were fed the same amount of supplement, adjusted daily to meet the ad libitum indoor intake of the cows at pasture for nine hours. The herbage allowance was 1650 kg dry matter (DM) per ha, and the intake of supplemental feed was 9.1 kg DM per cow daily. The limitation of the time at pasture to 4 h in combination with restrictive indoor feeding reduced the daily milk, fat and protein yield and live weight compared with 9 h of access to pasture. The proportion of time during which the cows were grazing while at pasture increased from 0.64 to 0.86 and the estimated herbage intake per h at pasture decreased from 2547 g DM to1398 g DM, when time at pasture changed from 4 to 9 h. It can be concluded, that in systems with a high herbage allowance, the cow was able to compensate for 0.8 of the reduction in time at pasture by increasing the proportion of time spent grazing and presumably also both the bite rate and mass, although the latter two have not been directly confirmed in the present study.     

Effects of rotational and continuous grazing on herbage quality,feed intake and performance of sheep on a semi-arid grassland steppe

Compared to continuous grazing (CG), rotational grazing (RG) increases herbage production and thereby the resilience of grasslands to intensive grazing. Results on feed intake and animal performance, however, are contradictory. Hence, the objective of the study was to determine the effects of RG and CG on herbage mass, digestibility of ingested organic matter (dOM), organic matter intake (OMI) and live weight gain (LWG) of sheep in the Inner Mongolian steppe, China. During June–September 2005–2008, two 2-ha plots were used for each grazing system. In RG, plots were divided into four 0.5-ha paddocks that were grazed for 10 days each at a moderate stocking rate. Instead, CG sheep grazed the whole plots throughout the entire grazing season. At the beginning of every month, dOM was estimated from faecal crude protein concentration. Faeces excretion was determined using titanium dioxide in six sheep per plot. The animals were weighed every month to determine their LWG. Across the years, herbage mass did not differ between systems (p = 0.820). However, dOM, OMI and LWG were lower in RG than in CG (p ≤ 0.005). Thus, our study showed that RG does not improve herbage growth, feed intake and performance of sheep and suggests that stocking rates rather than management system determine the ecological sustainability of pastoral livestock systems in semi-arid environments.     

划区轮牧中不同放牧利用时间对草地植被的影响

对比研究了划区轮牧中不同时间的放牧利用对各小区的植被状况的影响。结果表明 ,在固定放牧时间长度的情况下 ,早放牧小区的草群结构比晚放牧的小区受到的影响大。家畜对早放牧小区的牧草利用率高于晚放牧的小区 ,草地生产力则表现出相反的趋势。对于可利用牧草营养 ,早放牧的小区可提供较多的粗蛋白。在生产实践中 ,要灵活应用划区轮牧制度 ,对不同时间放牧利用的各小区要根据草地的实际情况来确定其具体的放牧时间长度 ,在不同的年度也要按不同的顺序来轮换放牧 ,兼顾到草地的可持续利用与家畜生产。     

Herbage intake and behavioural adaptation of grazing dairy cows by restricting time at pasture under two feeding regimes

The time at pasture of dairy cows is often restricted in the context of extending the grazing season in autumn or at the end of winter. The objective of our study was to evaluate the effects of a restriction of time at pasture on milk production, herbage intake and feeding behaviour in dairy cows according to feeding regime. The four treatments consisted of 4 h or 8 h of time at pasture per day tested under two feeding regimes combining rate of supplementation and herbage allowance: either a high rate of supplementation (10 kg dry matter (DM) of a maize silage-soya bean meal mixture in the ratio 87 : 13 on a % DM basis) with a low herbage allowance (6 kg DM/cow per day above 5 cm), or a low rate of supplementation (5 kg DM of the same supplement) with a high herbage allowance (11 kg DM/cow per day). The study was carried out according to a 4 × 4 Latin square design with four 2-week periods, with 48 mid-lactation Holstein cows. The cows in the 4-h treatment had access to pasture from 0900 h to 1300 h and those in the 8-h treatment from 0900 h to 1700 h. The supplement was given at 1830 h. When time at pasture was reduced from 8 h to 4 h per day, herbage intake decreased (9.9 v. 8.1 kg DM, P < 0.001), along with a fall in milk production (22.3 v. 21.2 kg, P < 0.001) and milk protein concentration (30.1 v. 29.6 g/kg, P < 0.001), while milk fat concentration increased (39.4 v. 39.9 g/kg, P < 0.05). The effect of time at pasture on milk production was slightly more marked on the low-supplement feeding regime (interaction P < 0.06). Reducing time at pasture by 4 h led to a sharp decrease in grazing time (327 v. 209 min, P < 0.001), but strongly increased the pasture intake rate (31 v. 39 g DM/min, P < 0.001) and the proportion of time spent grazing (0.68 v. 0.87, P < 0.001). Cows showed a stronger motivation for grazing when receiving the low-supplement feeding regime. In conclusion, we showed that reducing time at pasture from 8 to 4 h for cows receiving 5 to 10 kg DM of a maize silage-based supplement decreased moderately milk production and herbage intake, because of the capacity for behavioural adaptation by the grazing dairy cows.     

Determinations of feed–milk–manure relationships on grazing-based dairy farms

Feed conversion into milk, nutrient excretion in manure and subsequent environment impacts of manure management are highly influenced by the diets that farmers feed their lactating cows (Bos taurus). On confinement-based dairy farms, determinations of diet composition are relatively straightforward because the types, amounts and nutrients contained in stored feeds are often well known. However, on grazing-based dairy farms, diet composition is more difficult to determine because forage intake during grazing must be estimated. The objectives of this study were to determine relationships between (1) feed N intake (NI), milk production, milk urea N (MUN), feed N use efficiency (FNUE) and excreted manure N (ExN); and (2) between feed P intake (PI), dung P concentrations (g/kg dry matter (DM)) and excreted manure P (ExP) for grazing-based lactating cows having a very wide range of diets and milk production. An additional objective was to evaluate how well these relationships compare with similar relationships based on more direct measurement of feed–milk–manure on confinement-based dairy farms. Four dairy farms located in southeastern Australia were visited during autumn and spring, and data were collected on feed, milk and dung of 18 cows on each farm. Estimated dry matter intake (DMI) from pasture comprised 12% to 75% of total diet DMI, and the crude protein (CP) concentrations in the total diets ranged from 167 to 248 g/kg. During spring, as diet CP increased FNUE declined. Total diet DMI and NI provided the best predictors of ExN, and PI provided the most accurate prediction of ExP. These results indicated accuracy in the study's indirect estimates of pasture DMI. Likely due to high levels and great variability in dietary CP and P concentrations associated with use of diet supplements, MUN did not appear to be a good indicator of dietary CP, and P in dung was not a good indicator of dietary P.     

Changes in fatty acid profile of Bovec sheep milk due to different pasture altitude

Sheep rearing on mountain pastures is an ancestral tradition in northwestern Slovenia. The indigenous Bovec sheep are widespread there and are well adapted to the rough Alpine rearing conditions. Every year, after weaning, the sheep start grazing in the lowlands (L) and then gradually move to mountain pastures, and finally, to the highland (H) pastures of the Alps. Grazing positively affects the fatty acid (FA) composition in sheep milk fat with increased availability of polyunsaturated FA (PUFA) in grass, and subsequently, in milk. Consequently, the objective of this work was to study the FA profile in sheep milk during grazing in four geographical areas in the Alps. A total of 15 ewes of the Bovec sheep breed were randomly selected and milk samples from these ewes were taken at four different pasture locations that differed with regard to altitude: the L pasture location at an altitude of 480 m, the mountain pastures (M1 and M2) at altitudes of 1100 to 1300 m and 1600 to 1900 m, respectively, and the H pastures at altitudes of 2100 to 2200 m. Milk samples from the ewes were taken during the grazing season from April to September. The chemical and FA composition of the milk samples from each pasture location were determined. There were significant differences in the concentrations of FA among the L, M1, M2 and H milk samples. We observed decreases of the concentrations of saturated FA (SFA) in milk from L to H pastures. The concentration of α-linolenic FA, monounsaturated FA (MUFA), PUFA and n-3 PUFA in milk were increased significantly with pasture altitude. The n-6/n-3 PUFA ratio was reduced by the change of pasture altitude with the lowest value at the M1 pasture (1.5). The concentrations of total SFA decreased significantly and was lowest at the L pasture. Our results underline the importance of the effect of grazing in the Alpine region associated with pasture altitude on the FA profile of sheep milk. The first variation in FA concentration in sheep milk occurred between L and M1, although it was more evident on H pastures in the Alpine mountains. Changes of the FA profile in sheep milk due to pasture altitude were related to variation in FA concentration in the pasture and the botanical composition of the pasture location.     

Effect of pre-grazing herbage mass on dairy cow performance,grass dry matter production and output from perennial ryegrass (Lolium perenne L.) pastures

A grazing study was undertaken to examine the effect of maintaining three levels of pre-grazing herbage mass (HM) on dairy cow performance, grass dry matter (DM) production and output from perennial ryegrass (Lolium perenne L.) pastures. Cows were randomly assigned to one of three pre-grazing HM treatments: 1150 – Low HM (L), 1400 – Medium HM (M) or 2000 kg DM/ha – High HM (H). Herbage accumulation under grazing was lowest (P<0.01) on the L treatment and cows grazing the L pastures required more grass silage supplementation during the grazing season (+73 kg DM/cow) to overcome pasture deficits due to lower pasture growth rates (P<0.05). Treatment did not affect daily milk production or pasture intake, although cows grazing the L pastures had to graze a greater daily area (P<0.01) and increase grazing time (P<0.05) to compensate for a lower pre-grazing HM (P<0.01). The results indicate that, while pre-grazing HM did not influence daily milk yield per cow, adapting the practise of grazing low HM (1150 kg DM/ha) pasture reduces pasture DM production and at a system level may increase the requirement for imported feed.     

Effects of flaxseed,raw soybeans and calcium salts of fatty acids on apparent total tract digestibility,energy balance and milk fatty acid profile of transition cows

Oilseeds offer some protection to the access of ruminal microorganisms and may be an alternative to calcium salts of fatty acids (FA), which are not fully inert in the ruminal environment. This study aimed to evaluate the effects of different sources of FA supplementation on apparent total tract nutrient digestibility, milk yield and composition, and energy balance (EB) of cows during the transition period and early lactation. We compared diets rich in C18:2 and C18:3 FA. Multiparous Holstein cows were randomly assigned to receive one of the four diets: control (n=11); whole flaxseed (WF, n=10), 60 and 80 g/kg (diet dry matter (DM) basis) of WF during the prepartum and postpartum periods, respectively; whole raw soybeans (WS, n=10), 120 and 160 g/kg (diet DM basis) of WS during the prepartum and postpartum periods, respectively; and calcium salts of unsaturated fatty acids (CSFA, n=11), 24 and 32 g/kg (diet DM basis) of CSFA during the prepartum and postpartum periods, respectively. Dry cows fed WF had higher DM and net energy of lactation (NE_L) intake than those fed WS or CSFA. The FA supplementation did not alter DM and NDF apparent total tract digestibility, dry cows fed WF exhibited greater NDF total tract digestion than cows fed WS or CSFA. Feeding WS instead of CSFA did not alter NE_L intake and total tract digestion of nutrients, but increased milk fat yield and concentration. Calculated efficiency of milk yield was not altered by diets. FA supplementation increased EB during the postpartum period. Experimental diets increased long-chain FA (saturated and unsaturated FA) in milk. In addition, cows fed WS and CSFA had higher C18:1 trans-11 FA and C18:2 cis, and lower C18:3 FA in milk than those fed WF. Furthermore, cows fed CSFA had higher C18:1 trans-11 and cis-9, trans-11 FA than cows fed WS. Although supplemental C18:2 and C18:3 FA did not influence the milk yield of cows, they positively affected EB and increased unsaturated long-chain FA in milk fat.     

A model predicting the seasonal dynamics of intake and production for suckler cows and their calves fed indoors or at pasture

To investigate the dynamics of animal intake and production in grassland-based suckler systems, we constructed a model for suckling cows with their calves. The model calculates on a day-to-day basis the selective intake at pasture and the animal production (weight, condition, milk production) in response to energy intake. The model dynamically applies the feed evaluation systems developed by the INRA: the “cattle fill unit” system to predict forage intake, and the “feed unit” system to predict net energy requirements and supply. To predict intake at pasture, we adapted the cattle fill unit system by adding effects of herbage availability and sward structural composition on the amount and quality of intake.At pasture, the grazeable herbage is divided into structural components characterized by their biomass and digestibility. The model predicts the composition of the diet, assuming that the most digestible and abundant components of herbage are preferred. The amount of herbage ingested depends on the animal profile, the digestibility of the diet and the amount of herbage available. Sward depletion by animal intake at pasture has feedback effects on herbage growth and quality, which can be calculated by a vegetation model. Animal production is calculated based on net energy balance, which is the difference between net energy intake and net energy requirements for maintenance (for cow and calf), gestation and lactation (for the cow). The net energy balance determines weight and condition gain or loss, and – after 3 months of lactation – influences milk production the following day. Changes in weight and condition have feedback effects on energy requirements and intake capacity.Sensitivity analysis on the input values highlighted the importance of forage digestibility for the production of cows and calves. Calf growth was also driven over 3 months old by calf live weight, and under 3 months old by the milk production of the cow. The model's response to stocking rate during the grazing down of a paddock was consistent with current knowledge. The model was validated against experimental data for cows fed indoors or at pasture, at different feed allowances. Model predictions were precise for the digestibility of intake and for live weight (error represents 2–3% of the average observed value), satisfactory for dry matter intake, body condition score and milk production at the beginning of lactation (error represents 10% of the average observed value), and very imprecise for milk production after the third month of lactation (error represents 23% of the average observed value), but the latter had small consequences on calf live weight.     

Monitoring and assessment of ingestive chewing sounds for prediction of herbage intake rate in grazing cattle

Accurate measurement of herbage intake rate is critical to advance knowledge of the ecology of grazing ruminants. This experiment tested the integration of behavioral and acoustic measurements of chewing and biting to estimate herbage dry matter intake (DMI) in dairy cows offered micro-swards of contrasting plant structure. Micro-swards constructed with plastic pots were offered to three lactating Holstein cows (608±24.9 kg of BW) in individual grazing sessions (n=48). Treatments were a factorial combination of two forage species (alfalfa and fescue) and two plant heights (tall=25±3.8 cm and short=12±1.9 cm) and were offered on a gradient of increasing herbage mass (10 to 30 pots) and number of bites (~10 to 40 bites). During each grazing session, sounds of biting and chewing were recorded with a wireless microphone placed on the cows’ foreheads and a digital video camera to allow synchronized audio and video recordings. Dry matter intake rate was higher in tall alfalfa than in the other three treatments (32±1.6 v. 19±1.2 g/min). A high proportion of jaw movements in every grazing session (23 to 36%) were compound jaw movements (chew-bites) that appeared to be a key component of chewing and biting efficiency and of the ability of cows to regulate intake rate. Dry matter intake was accurately predicted based on easily observable behavioral and acoustic variables. Chewing sound energy measured as energy flux density (EFD) was linearly related to DMI, with 74% of EFD variation explained by DMI. Total chewing EFD, number of chew-bites and plant height (tall v. short) were the most important predictors of DMI. The best model explained 91% of the variation in DMI with a coefficient of variation of 17%. Ingestive sounds integrate valuable information to remotely monitor feeding behavior and predict DMI in grazing cows.     

Seasonal and interannual variations in feeding station behavior of cattle: effects of sward and meteorological conditions

A feeding station is the area of forage a grazing animal can reach without moving its forefeet. Grazing behavior can be divided into residence within feeding stations (with bites as benefits) and movement between feeding stations (with steps as costs). However, relatively little information has been reported on how grazing animals modify their feeding station behavior seasonally and interannually in response to varying environmental conditions. The feeding station behavior of beef cows (Japanese Black) stocked on a tropical grass pasture (bahiagrass dominant) was monitored for 4 years (2010 to 2013) in order to investigate the association of feeding station behavior with meteorological and sward conditions across the seasons and years. Mean air temperature during stocking often exceeded 30°C during summer months. A severe summer drought in 2013 decreased herbage mass and sward height of the pasture and increased nitrogen concentration of herbage from summer to autumn. A markedly high feeding station number per unit foraging time, low bite numbers per feeding station and a low bite rate were observed in summer 2013 compared with the other seasons and years. Bite number per feeding station was explained by a multiple regression equation, where sward height and dry matter digestibility of herbage had a positive effect, whereas air temperature during stocking had a negative effect (R²=0.658, P<0.01). Feeding station number per minute was negatively correlated with bite number per feeding station (r=–0.838, P<0.001). It was interpreted that cows modified bite number per feeding station in response to the sward and meteorological conditions, and this largely determined the number of feeding stations the animals visited per minute. The results indicate potential value of bite number per feeding station as an indicator of daily intake in grazing animals, and an opportunity for livestock and pasture managers to control feeding station behavior of animals through managements (e.g. fertilizer application, manipulation of stocking intensity and stocking time within the day).     

Control of nematode parasites by grazing management—II. Decontamination of sheep and cattle pastures by varying periods of grazing with the alternate host

Commencing in December 1970, paddocks of a uniform series of sheep pastures were grazed for 6, 12 or 24 weeks by either yearling steers is or yearling ewes. Cattle pastures were treated similarly. All ewes and steers were pre-dosed with anthelmintic.At the conclusion of alternate grazing the effectiveness of the grazing treatments was evaluated by grazing each paddock for 1 month with either ten worm-free lambs (sheep pastures) or three wormfree calves (cattle pastures). The test animals were then slaughtered for total worm counts. The grazing of sheep pastures with cattle for 6, 12 or 24 weeks from December onwards resulted in reductions in numbers of Haemonchus contortus and Trichostrongylus colubriformis in test lambs. In comparison with continuous grazing by sheep, Nematodirus spp was only reduced after 24 weeks grazing by cattle. Cattle pastures grazed by sheep for 6 weeks showed no reduction in numbers of Ostertagia ostertagi or Cooperia oncophora in test calves. However after 12 weeks with sheep, numbers of O. ostertagi though not C. oncophora were reduced and after 24 weeks of alternate grazing both these species were reduced.Calves following the 6 week sheep treatments acquired both Haemonchus contortus and Trichostrongylus colubriformis and the calves from the 12 week sheep treatment paddock also carried H. contortus. For sheep the only evidence of cross-transmission was the occurrence of small numbers of Cooperia oncophora in test lambs from the 24 week cattle grazing treatment.The results provide evidence that sequential stocking with cattle and sheep in conjunction with anthelmintic treatment is an effective management strategy for preparing parasitologically safer pastures, but further information is required to determine the optimum timing of sequential stocking in farming situations.     

Fine-scale spatial distribution of herbage mass,herbage consumption and fecal deposition by cattle in a pasture under intensive rotational grazing

Herbage mass, herbage consumption and fecal deposition by animals were monitored for 2 years in 182 fixed locations (0.5 × 0.5 or 1 × 1 m) in a sown pasture (1.1 ha) grazed rotationally by cattle (42–45 animals). Fecal deposition was more spatially variable (higher values of coefficient of variation) than herbage mass and consumption, with consistently significant bias from the normal distribution in both skewness and kurtosis. In terms of spatial pattern, herbage mass and consumption were always or almost always spatially heterogeneous (nonrandom spatial pattern), while fecal deposition was less frequently heterogeneous or usually homogeneous (random spatial pattern). The spatial heterogeneity in herbage mass was interpreted as being created in the early grazing season possibly through spatial heterogeneity in soil-related factors, and maintained until the late grazing season mainly by herbivory where the animals always left more herbage uneaten at locations with higher pre-grazing herbage mass. Even when cumulated for 2 years (56 days of grazing), herbage consumption and fecal deposition were still considerably spatially variable. Such nonuniform cumulation of animal impacts, however, is not likely to have a negative effect on the grazing system (paddock as the major grazing area) because (1) the animals almost always consumed more herbage from locations with higher herbage mass, resulting in a less variable degree of utilization (consumption/production) across the paddock; (2) fecal deposition on the paddock was not abundant, due to the concentration of feces in the resting area adjoined; and (3) fertilizer was regularly applied to the paddock as management.